1. Field of the Invention
This invention relates to a system for controlling emissions in an internal combustion engine and, more particularly, to use of a silicon carbide sensor to measure flame temperature at each cylinder of an internal combustion engine for controlling fuel injection.
2. Description of the Related Art
Silicon carbide (SIC) is a crystalline substance that can withstand very high temperatures. For example, semiconductor devices manufactured of SiC can withstand temperatures in excess of 300.degree. C. Thus, SiC semiconductors are desirable for applications that require exposure to high temperatures.
SiC electronics technology can be viewed as a means of controlling flame temperature by reducing fuel-to-air ratios in high temperature environments, such as encountered in the internal combustion of an automobile, which reduces the production of nitrogen oxide (NO.sub.x) emissions. When the operating temperature is excessively high, NO.sub.x emissions, which are classified as pollutants, are also excessively high. However, when fuel is burned lean to hold down the flame temperature, the flame can produce too much carbon monoxide (CO) and become unstable or even be extinguished with resulting exhaust contamination of unburned fuel. The design constraints for these combustion engines have become so exacting that the manufacturing tolerances are difficult to achieve.
In conventional internal combustion engines, the fuel-to-air ratio is controlled in an open loop manner by sensing the total air input. Combustion occurs, however, in each of the cylinders. Conventional internal combustion engines are therefore subject to errors caused by an imbalance of the fuel-to-air ratios in different cylinders even when the total air input value is within the correct range.